Conventionally, there has been used an engine speed display device for displaying an engine speed of a vehicle. The engine speed display device controls an engine speed display unit (a tachometer or a revolution counter) which displays an engine speed in accordance with an engine speed signal output from an engine speed sensor which detects the engine speed.
The engine speed signal varies while reflecting a subtle variation of the engine speed or a detection variation of the engine speed sensor. Therefore, causing the engine speed display unit to directly display a variation of the engine speed signal may result in continuous display of a subtle variation of the engine speed. This may lower the visibility.
In view of the above, in order to prevent lowering of the visibility, there is proposed a configuration, in which the display responsiveness of the engine speed display unit with respect to an engine speed signal output from the engine speed sensor is intentionally lowered.
For instance, Patent Literature 1 discloses a vehicle engine speed display device which determines the engine speed to be displayed on a display unit on the basis of engine speed signals to be output during a predetermined determination time period. The vehicle engine speed display device shortens the determination time period, as the engine speed increases. Specifically, the determination time period is extended when the engine is in a low speed condition. This makes it possible to lower the display responsiveness of the engine speed display unit with respect to an engine speed signal to thereby prevent a subtle variation of display. On the other hand, the determination time period is shortened when the engine is in a high speed condition. This makes it possible to enhance the display responsiveness of the engine speed display unit with respect to an engine speed signal. Thus, it is possible to carry out the display, while following a variation of the engine speed.
Further, Patent Literature 2 discloses an operation state display device of an internal combustion engine, in which an intended display operation is carried out in accordance with the driver's will by enhancing the display responsiveness of a tachometer when an accelerator pedal is operated by a predetermined amount or when a gear shift operation is performed in the manual gear shift mode.
A driver who drives a vehicle installed with a high-performance engine expects a sharp change in the engine speed at the time of a gear shift operation to make sure that the engine has high efficiency. At the time of a gear shift operation, the driver not only audibly perceives an engine speed change by the engine sound but also tries to visually perceive the change by a display change of the engine speed display unit.
However, the device disclosed in Patent Literature 1 is proposed to enhance the display responsiveness of the engine speed display unit, as the engine speed increases, and does not take into account whether it is the time of gear shift operation. Therefore, when the gear shift operation is performed when the engine in a low speed condition, the engine speed display unit may fail to fully display a sharp change in the engine speed.
Further, the device disclosed in Patent Literature 2 is proposed to enhance the display responsiveness of a tachometer throughout the whole period from the time when the gear shift operation is started by a gear shift command to the time when the gear shift operation is terminated. Therefore, the display responsiveness enhances not only in a period when the engine speed is changed by the gear shift operation but also in a period other than the above. This may make the engine speed change by the gear shift operation unclear.
As described above, in the conventional devices, it is difficult to control the engine speed display unit to display the engine speed in such a manner that a sharp change in the engine speed at the time of a gear shift operation is made clear.